Gurukrishna K
@jncasr.ac.in
Postdoctoral Research Associate
Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR)
RESEARCH INTERESTS
Electronic materials, Transport phenomena
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
N. P. Madhukar, K. Gurukrishna, Bhoomika R. Bhat, U. Deepika Shanubhogue, Suraj Mangavati, Ashok Rao, and Saikat Chattopadhyay
Springer Science and Business Media LLC
AbstractThe influence of sintering temperature on the thermoelectric (TE) transport of BiCuSeO is reported in the present work, with an aim to optimize the processing conditions for higher TE transport. BiCuSeO samples were synthesized at four different sintering temperatures, viz., 673 K, 773 K, 873 K, and 973 K. A non-degenerate type of conductivity is observed in all the samples at high temperatures, witnessing the thermal activation of the carriers. The Fermi level was positioned below the valence band maximum, thereby exhibiting a p-type degenerate transport in the entire range of temperature. It was observed that the variations of weighted mobility and power factor were found to have identical trends. The highest power factor was noticed at 554 K with a value of 129 μWm−1 K−2 for the sample sintered at 673 K.
K. Gurukrishna, Ashok Rao, Shyam Prasad K, Yu-Chun Wang, and Yung-Kang Kuo
Elsevier BV
Ganesh Shridhar Hegde, A. N. Prabhu, Suchitra Putran, Ashok Rao, K. Gurukrishna, and U. Deepika Shanubhogue
Springer Science and Business Media LLC
AbstractBy using the solid-state reaction approach, composite polycrystalline samples of (Bi0.98In0.02)2Te2.7Se0.3/x%Bi2Se3 were created with varying amounts of Bi2Se3, (x = 5%, 10%, 15%, and 20%). The hexagonal crystal structure of the composite was revealed by x-ray diffraction (XRD) with a space group of R$$\\overline{3 }$$ 3 ¯ m. The surface of the samples was seen to have secondary particles using a field emission scanning electronic microscope. Every sample displayed the typical semi-conducting behaviour across the entire temperature range. In the complex (Bi0.98In0.02)2Te2.7Se0.3, it was found that bismuth was coordinated with six selenium atoms and there were significant selenium vacancies. With an increase in bismuth selenide concentration, the dissolution pattern shifted to a substitutional pattern. A two fold decrease in electrical resistivity for (Bi0.98In0.02)2Te2.7Se0.3/20%Bi2Se3 composition was seen compared to (Bi0.98In0.02)2Te2.7Se0.3/5%Bi2Se3. The granular material was produced by sintering and scattering of potential barrier, a thermal process that increases the Seebeck coefficient. A 200% increase was observed in thermopower for (Bi0.98In0.02)2Te2.7Se0.3/20%Bi2Se3 compared to (Bi0.98In0.02)2Te2.7Se0.3/5%Bi2Se3 compound. Graphical Abstract
Anand Pal, K. Shyam Prasad, K. Gurukrishna, Suraj Mangavati, P. Poornesh, Ashok Rao, Yin-Chun Chung, and Y.K. Kuo
Elsevier BV
R. Bhat. Bhoomika, K. Gurukrishna, N. P. Madhukar, U. Deepika Shanubhogue, Ashok Rao, Ruei-Yu Huang, Yung-Kang Kuo, and K. K. Nagaraja
Springer Science and Business Media LLC
AbstractWe herein report on compositing highly conductive GdH2 with BiCuSeO, with an aim to modulate the electronic transport and the nature of conductivity in the high-temperature regime. The incorporation of GdH2 as a minor matrix in BiCuSeO, as confirmed by structural studies, has considerably enhanced electrical conductivity in the system, thereby demonstrating the existence of thermal activation of the charge carriers. The effect of minor matrix is directly on the conversion of p-type to n-type conductivity in BiCuSeO system at near room temperature. Electronic quality factor (BE) has identified the ambiguities in the transport behaviour at near room temperature due to the addition of minor matrix. Enhancement in the power factor is seen due to GdH2, with a highest attained value of 221 μW m K−2 at 700 K for the sample with x = 11 wt%, which is nearly twice the value of pristine BiCuSeO. Highest ZT of 0.011 is obtained for the pristine BiCuSeO sample at 380 K.
Suraj Mangavati, K Gurukrishna, Ashok Rao, Vikash Chandra Petwal, Vijay Pal Verma, and Jishnu Dwivedi
Springer Science and Business Media LLC
AbstractThe modification in the Cu2Se thermoelectric system by electron beam irradiation has been carried out in this work. Samples were prepared using the solid-state reaction technique. The prepared samples were irradiated with various energy dosages viz. 50, 100, and 150 kGy. XRD studies reveal that the synthesized samples crystallized in a monoclinic structure. The micro-hardness of the samples decreased with an increase in irradiation dosage. The sample irradiated at 100 kGy dose exhibits the lowest electrical resistivity, moderate Seebeck coefficient, and highest power factor.
Ramakrishna Nayak, Prakasha Shetty, Selvakumar M, Ashok Rao, K. Mohan Rao, Gurukrishna K, and Suraj Mangavati
Elsevier BV
Ganesh Shridhar Hegde, A. N. Prabhu, Ashok Rao, K. Gurukrishna, and U. Deepika Shanubhogue
Springer Science and Business Media LLC
AbstractPolycrystalline composite samples of (Bi0.98In0.02)2Se2.7Te0.3/Bi2Te3 with different concentrations of Bi2Te3 such as 5%,10%,15% and 20% were prepared by the solid-state reaction technique. The X-Ray diffraction analysis has shown the hexagonal composite crystal structure with space group of $$R\\overline{3 }$$ R 3 ¯ m. Field emission scanning electronic microscope shows secondary particles on the surface of the samples. All the samples have shown the usual semi-conducting behaviour throughout the temperature range. It is observed that bismuth has been co-ordinated with 6 selenium atoms in (Bi0.98In0,02)2Se2.7Te0.3 compound and it has enormous selenium vacancies. The electrical resistivity represents the noteworthy result of the grain boundaries leading to the higher content of scattering centres in the polycrystalline composite samples. It is found that the electronegativity differences of In and Te, In and Se are less than Bi and Se, Bi and Te is the reason for the decrease in Seebeck coefficient in the compound containing 15% and 20% of Bi2Te3.
K. Gurukrishna, Suraj Mangavati, Ashok Rao, P. Poornesh, Vikash Chandra Petwal, Vijay Pal Verma, and Jishnu Dwivedi
Springer Science and Business Media LLC
AbstractWe present report on modulating thermoelectric transport in Cu2SnSe3system via irradiating high-energy electrons of energy of about 8 MeV. Electrical transport is investigated at near room to mid-temperature regime (300–700 K). A smooth transition from degenerate to non-degenerate type of conductivity is observed in all the samples, which indicates the injection of minority carriers with ionisation of defects at high temperatures. Defects created through the knock-on displacement of the constituent atoms is successful in promoting the power factor in the material. Cu2SnSe3irradiated with 50 kGy is found to achieve highest power factor of 228 µW/mK2at 700 K, which is nearly 20% higher than the power factor of pristine material at the same temperature.
K. Gurukrishna, H. R. Nikhita, S. M. Mallikarjuna Swamy, and Ashok Rao
Springer Science and Business Media LLC
AbstractA detailed investigation on the temperature dependent electrical properties of Cu2SnSe3 system, synthesized via conventional solid-state reaction at different sintering temperatures are presented in this communication. All the samples exhibit degenerate semiconducting nature at low temperatures. The existence of small polarons and hence electron–phonon interactions are confirmed at temperatures below 400 K. A transition was observed from degenerate to non-degenerate semiconducting behaviour at high temperatures (T > 400 K). The study confirms the unusual transition in electrical resistivity as well as thermopower at high temperatures in all the compounds, demonstrating the existence of minority carrier excitation along with temperature-triggered ionisation of the defects. The transport behaviour is further supported by an upward movement of Fermi level away from the valence band. Highest weighted mobility of 8.2 cm2 V−1 s−1 at 673 K was obtained for the sample sintered at 1073 K. A considerable decrease in electrical resistivity with increase in temperature (T > 400 K) has driven the power factor to increase exponentially, thereby achieving highest value of 188 µV/mK2 (at 673 K) for the sample sintered at 673 K. Graphic abstract
K. Gurukrishna, Ashok Rao, Yin-Chun Chung, and Yung-Kang Kuo
Elsevier BV
K. Gurukrishna, Ashok Rao, Zhao-Ze Jiang, and Yung-Kang Kuo
Elsevier BV